Equine diarrhoea Flashcards
Where is the major site of water absorption in the horse?
Large colon
Describe the normal faeces of a horse
Formed droppings
8-10 times / day
10-15kg / day
75% water
What is diarrhoea?
Increased volume / frequency and fluidity of faeces
Name the 5 mechanisms of diarrhoea
- Malabsorption
- Increased secretion
- Osmotic overload
- Abnormal motility
- Extravasation of fluid (oedema)
How does malabsorption cause diarrhoea?
Loss of absorptive cells / tight junctions
Often inflammation
How does increased secretion occur which leads to diarrhoea?
Intracellular cAMP / Ca Bacterial exotoxins Inflammation
What are the causes of an osmotic overload?
Feeds / additives Malabsorption
e.g. Mag. sulphate
Where is acute diarrhoea in the horse localised?
Colitis
= inflammation of the colon or inflammation of the caecum and colon
Inflammation of the caecum and colon is termed?
Typhlocolitis
How is localisation of where diarrhoea occurs different in adult horses and foals
In adults (not foals): colon very effective at absorbing water - LI is always affected, disease of only the SI does not cause diarrhoea In foals: Diarrhoea can occur with just SI disease
Which substances are lost from the body with diarrhoea?
Water - dehydration
Electrolytes - electrolyte derangements
Protein - hypoproteinaemia
Which horses are affected by chronic diarrhoea?
All breeds
All ages
Describe chronic diarrhoea in horses
- Any diseases that cause acute diarrhoea can progress to chronic diarrhoea
- Many of the conditions considered for weight loss will also cause diarrhoea
- In horses, diarrhoea will only occur if there is extensive colonic pathology
- There can be colonic pathology without diarrhoea
What are some differential diagnosis for chronic diarrhoea in the adult horse?
- Dietary causes: abnormal fermentation
- Dental disease
- Parasitism e.g. strongylosis
- Sand ingestion
- Antimicrobial associated
- NSAID toxicity
- Non-GI causes e.g. kidney, liver, heart
- Neoplasia
- Infiltrative disorders
Describe the information that should be gathered from a horse with chronic diarrhoea
- management of the horse
- normal diet and recent diet changes
- exercise, travel, other causes of stress
- deworming strategies and other concurrent therapies
- history of recurrent episodes
- diarrhoea in contact animals
What clinical signs might a horse with chronic diarrhoea show?
- No/Mild dehydration
- Bright/Eating well (NOT SIRS)
+/- Weight loss
+/- Polydipsia
+/-Oedema
What needs to be ruled out if a horse is pyrexic? How?
Salmonella, Coronavirus (5 faecal samples for culture, PCR faeces /isolate till sure)
Which diagnostics can be carried out to help diagnose the cause of chronic diarrhoea?
- Check for parasites
- Check haematology and biochemistry for inflammation
- Check plasma protein concentration
- Peritoneal fluid
- Ultrasound
- Rectal biopsy
- Absorption tests
Name two parasites groups of horses that can cause diarrhoea?
Ascarids
Cyathostomins
How can chronic diarrhoea be treated?
- Treat underlying disease
- Lavicidal deworm: Fenbendazole or ivermectin
- Yeast/probiotic
- Access to normal manure
- Anti diarrhoea medications (usually ineffective long-term)
What does SIRS stand for?
systemic inflammatory response syndrome
What are some important causes of acute diarrhoea in horses > 9 months old?
- Idiopathic* most common
- Salmonella
- Clostridia
- Drug-induced: antibiotics
What are some predisposing factors for acute diarrhoea?
Antibiotic treatment Transport Competition Hospitalisation Surgery ANY STRESS
What are the two main presenting signs of a horse with acute diarrhoea?
Depression
Fever
What are some other presenting signs in a horse with acute diarrhoea?
Tachycardia (80-100 bpm) Tachypnoea Congested to purple mm’s Slow CRT >2s Anorexia Dehydration Reduced GI sounds Colic Diarrhoea
What are 3 causes of fluid loss in acute diarrhoea?
- Excess secretion due to inflammation + enterotoxins
- Malabsorption
- Loss of Na, Cl, K, bicarb and albumin
Describe the pathophysiology of acute diarrhoea
- Fluid loss
- Mucosal inflammation, ischaemia and reperfusion injury
- Breakdown of GI mucosal barrier
Describe the pathophysiology of SIRS
- Inflamed colon -> toxins (bacterial)
- Go into the hepatic portal vein
- Overwhelm normal mechanisms of clearance in the liver
- Enter systemic circulation
Which organs/tissues are affected by SIRS
- Endothelium: thrombosis, phlebitis especially JUGULAR
- Gastrointestinal
- Integument: equine hoof laminae -> laminitis
- Kidneys
Name the infectious causes of acute diarrhoea
- Salmonella
- Clostridium perfringes and difficile
- Coronavirus
What is the source of infection of infectious acute diarrhoea?
Asymptomatic shedders or diseased horses
Name some environmental and host stressors
- High ambient temperature
- Hospitalisation
- Transport
- Antibiotics
- Gastrointestinal surgery
- Immunosuppression
What are the effects of cytotoxins?
Morphological damage and increase penetration of mucosa
What are the effects of enterotoxins?
Increase sodium and water secretion
Which clinical syndromes are linked to infectious diarrhoea?
- Cytotoxins
- Enterotoxins
- Marked neutropaenia, hyponatraemia and dehydration
- Septicaemia
Describe antibiotic induced diarrhoea
- Any antimicrobial
- E.g. Mares with foals receiving erythromycin
- Allows overgrowth of pathogens or poorly understood dysbiosis in colon
What are the aims when taking a diagnostic approach to acute diarrhoea cases
Determine need for supportive therapy
Determine risk to in-contact horses:
- Salmonellosis: Faecal culture
- Clostridial: Cl. perfringens and difficile toxin assays
- Coronavirus: PCR
- ISOLATE till results are proven negative
Describe the treatment approach for horses with acute diarrhoea
- Determine need for fluid therapy
- Determine hypovolaemia / dehydration
- Assess electrolyte / albumin / acid-base status
Describe the effects of increasing % dehydration on the body
- Increasing HR
- Increasing CRT
- Increase in PCV and total protein
- Increased creatinine
- Dry mm, sunken eyes, signs of shock if severe
How is existing volume deficit calculated?
% dehydration X body weight
Aim to replace over first 4-6 hrs (LRS)
Add: Colloids / plasma if hypoalbuminaemic
Which solution should be given in a severe hypovolaemic case?
Hypertonic saline
Describe some treatments for acute diarrhoea
- Determine need for colloids
- Determine need for additional electrolytes
- Always offer electrolyte solutions as well as fresh water
- Don’t forget to offer food
Describe monitoring of a patient with acute diarrhoea
- Repeat clinical assessments regularly
- Monitor electrolyte concentrations
- Cumulative fluid volumes per hour and per 12 and 24 hours essential to be calculated
Describe supportive therapy for a horse with acute diarrhoea
- Treat SIRS: NSAIDS
- Ice feat against laminitis
- Oral protectants
